The present invention relates to a method and system for securing offshore vessels and structures and, more particularly, to anchoring offshore drilling and/or production vessels in relation to the ocean floor.
Surface facilities must be maintained in position over a well site for offshore drilling operations and often for production operations. This often requires the deployment of an array of mooring lines, each anchored to the seabed with a pile foundation or the like. Installing such foundation elements for secure anchorage is time consuming and requires considerable offshore equipment.
Another problem arising in deepwater is that the spread of these mooring lines can be substantial and anchor structures are widely placed over a leasehold or even into adjacent lease blocks and the mooring arrays of adjacent blocks can overlap. Further, the sequential steps in development such as exploration wells, test wells, satellite subsea wells, etc. can each leave foundation elements until the seafloor actually becomes crowded in relation to the necessary infrastructure for working offshore prospects.
Suction anchors as disclosed in U.S. Pat. No. 4,318,641 have been known as a method for installing tubular elements into the seabed. This provides an alternative to driving or drilling and grouting piles and provides opportunity for easier installation, but the installation is remains equipment intensive and does not facilitate foundation removal.
Thus, there remains a need for a method and system for anchoring offshore structures and vessels which further facilitates ease of deployment with a minimum of equipment.
One aspect of the present invention is a method for deploying a suction pile anchor in which flood valves are opened on the top of a suction pile and the suction pile anchor is off loaded from the anchor boat and lowered it to the sea floor. The suction pile anchor is set down and the rate of feed is adjusted to match the rate of self-penetration. An ROV with pump capability closes the flood valves on the top of the suction pile and attaches to the pump port of the suction pile. The pump of the ROV operates to draw down the suction pile to full depth and brings the load pad-eye and the attached first end of the load line well below the mudline while the load connection at the second end of the load line is supported above the mudline. The ROV disconnects from the pump port and connects a mooring line to the load connection.
Another aspect of the present invention is a suction pile system having a suction pile with an ROV compatible pressure port and a flood valve at the top. A load support system includes a first load connection on the side of the suction pile with a load line connected to the first load connection and a second load connection connected to the end of the load line. An installation support system is included having an installation connection on the top of the suction anchor pile.